1. Field of the Invention
This invention generally relates to a liquid crystal display, and more particularly, to a transflective liquid crystal display.
2. Description of the Related Art
Generally, a transmissive liquid crystal display (LCD) device has advantages of high contrast ratio and good color saturation. However, the transmissive LCD device may suffer low image contrast when ambient light is strong. In addition, its power consumption is high due to the need of a backlight device. On the other hand, a reflective LCD device uses ambient light, instead of backlight, for displaying images, and therefore its power consumption is relatively low. However, the reflective LCD device is less visible when ambient light is weak.
In order to overcome the above-mentioned drawbacks, a transflective LCD device is developed. The transflective LCD device can use both the back light and ambient light so that it can perform a clear display even in dark surroundings while reducing the power consumption. In general, the transflective LCD device includes two types, i.e. a single cell gap transflective LCD device and a double cell gap transflective LCD device. In the single cell gap transflective LCD device, the cell gaps for reflective and transmissive regions are the same. In the double cell gap transflective LCD device, the cell gaps for reflective and transmissive regions are different.
Referring to FIG. 1, a conventional double cell gap transflective LCD 100 includes two polarizers 132, 134 and two compensation films 122, 124 disposed between the polarizers 132, 134. Two substrates 112, 114 are disposed between the compensation films 122, 124 and a liquid crystal layer 140 with a thickness of d is sandwiched between the substrates 112, 114. A reflection plate 150 with a plurality of openings is disposed on the substrate 114. The light 160 from a backlight (not shown) passes through in sequence the substrate 114, the openings of the reflection plate 150, liquid crystal layer 140 and ultimately arrives at a viewer. In addition, the ambient light 170 passes through the substrate 112, liquid crystal layer 140 and is ultimately reflected to the viewer by the reflection plate 150. In order to make the light 160 and ambient light 170 have the same optical path length when they pass through the liquid crystal layer 140, it is necessary for the reflection plate 150 to have a thickness equal to one-half of that of the liquid crystal layer 140, i.e. d/2. However, extra facilities are required for manufacturing the reflection plate 150 in the LCD 100 and the production yield in manufacturing the same is remarkably reduced.
Referring to FIG. 2, a conventional mixed-mode twisted nematic (MTN) single cell gap transflective LCD 200 also includes a reflection plate 150′ with a plurality of openings thereon. In comparison with the LCD 100, the LCD 200 is required to have a 90-degree difference in pretilt angle between the alignment layers 282 and 284 that are disposed respectively on the transmissive region and reflective region. This will need more complicated processes to make such a structure.
Referring to FIG. 3, another conventional mixed-mode twisted nematic single cell gap transflective LCD 300 has a quarter-wave retardation film 390 disposed on the reflection plate 150′ in order to compensate for the optical path length. Likewise, it is also required to have extra facilities for making such a structure.
In view of the above, there exists a need to provide a transflective liquid crystal display to solve the above-mentioned problems.